1. Field of the Invention
The present invention relates to detection of occurrence of a fault in a network.
2. Description of the Related Art
In a system configuration where two communication devices (for example, layer 2 switches) are connected with each other via a network, two bidirectional paths (communication paths) are established between the two communication devices. When a fault occurs in one of the two paths (called “unidirectional path fault”), various problems arise; for example, frame looping on the network. UDLD (Unidirectional Link Detection) protocol has been proposed for detection of such a unidirectional path fault (Cisco System Unidirectional Link Detection (UDLD) Protocol (RFC:5171), Cisco Systems, April 2008, Retrieved from the Internet; on Jun. 20, 2010).
According to the UDLD protocol, each of the two communication devices sends a link health check frame to the other communication device and detects the occurrence of a unidirectional link fault based on reception or non-reception of a link health check return frame sent back from the other communication device.
The UDLD protocol applies the software configuration to analyze various parameters included in the received frame and detects the occurrence of a unidirectional path fault based on the result of the analysis. This arrangement requires a relatively long time for detection of a fault. It is thus desired to shorten the time period required for detecting a unidirectional path fault.